It is well known in the medical arts to provide structures such as inflatable balloons, stents, stent grafts, grafts, and the like disposed concentrically on a distal end of a catheter. Such structures serve a variety of useful purposes, such as widening a vessel having an interior lumen (for example, a blood vessel) into which the catheter is inserted, forcing open a blocked or partially blocked vessel, delivering a stent, graft, or stent graft to a desired section of a vessel for unblocking or repair purposes, and the like. The dimensions and properties of such structures (length, thickness, flexibility and the like), and the materials from which they are fabricated, vary widely in accordance with the intended use thereof.
Using the balloon catheter as an example, it is desirable for the balloon, when in the deflated state, to define a low profile configuration, conforming to the exterior dimensions of the catheter distal end, for lesion crossability, trackability, and overall deliverability of the catheter. That is, it is desirable for the balloon, which is folded on and concentrically disposed around an exterior surface of the catheter, to increase the cross-sectional dimension of the catheter/balloon assembly as little as possible when deflated. This preserves the flexibility of the catheter and improves catheter tracking and deliverability of the catheter, particularly at the distal end on which the balloon is disposed, and reduces the potential for damage to the vessel wall during insertion/retraction of the catheter. Similarly, this minimizes introducer sheath compatibility.
To achieve this and other goals, it is known to define a pattern of indentations such as grooves, channels, relief structures, and the like (termed “checkering”) on an exterior of a structure wrapped concentrically about a catheter, such as for example a deflated balloon, a stent, a graft, a stent graft, or the like. Upon inflating the balloon, such as with sterile saline or the like passed through the catheter lumen and therefrom into an interior of the balloon, the indentations substantially disappear as the balloon inflates. Upon deflating the balloon, the indentations reform, and may assist the balloon in reverting to the former, low profile configuration about the catheter. This reversion to the low profile configuration may assist in refolding of the device for reinsertion.
Such indentations may be molded, cut, or carved into the exterior surface of the balloon. However, this method increases labor and manufacturing costs. More desirably, the surface pattern of indentations may be defined in or on that exterior structure by winding a suitable material, such as a tape, beading, wire, fiber, filament, or the like around an exterior surface of the balloon, and applying heat and pressure to create the desired pattern of indentations. Prior winding methods for providing such a pattern of indentations, primarily involving manual winding, do not satisfactorily address quality control issues. Particularly, such manual methods do not provide suitable consistency in terms of tension applied to the filament, and also do not provide consistent catheter-to-catheter results in terms of the pitch of the wound line and the resulting pattern. Still further, heat and pressure-applying devices known ill the prior art for catheter manufacture require constant re-adjusting/re-tooling to accommodate catheters of different lengths.
The present disclosure addresses a need in the art for methods and devices for providing such a pattern of surface indentations in an exterior surface of a balloon, stent, graft, stent graft, or combination thereof disposed concentrically about the distal tip of a catheter. In particular, improved methods and devices for automating the process of providing such surface indentations are disclosed. Even more, the present disclosure provides methods and devices for not only automating the process, but also for accommodating catheters of substantially any length without need for reconfiguration of the device. The presently disclosed invention meets this need in the art, while also contemplating good engineering practices, including relative inexpensiveness, stability, ease of implementation, low complexity, etc.